Invasion
Experts fear weevil impact on dates
Date growers in the Yuma area produce about 10 million pounds a year, a $30 to $35 million dollar industry that employs more than 2,000 people annually, according to Visit Yuma. The agency noted that thanks to ideal soil and weather, the area around Yuma and Bard, Calif., is now the world’s largest producer of premium-quality Medjool dates.
Unfortunately, that industry could be wiped out if the South American palm weevil makes its way to the area.
The weevil has killed hundreds of Canary Island palm trees in southern San Diego County in California. Although it’s been killing mostly ornamental palms in urban areas, experts worry the pest could invade California’s date production areas in the Coachella Valley. They noted that if the South American palm weevil behaves similarly to its close relative, the red palm weevil, the impacts on date production in California and Arizona could be significant.
The U.S. Department of Agriculture trapped the insect in Yuma in May 2015. However, it is not known if this weevil has established in Arizona. The agency recently found another one but it was dead. The USDA is carefully monitoring for the pest and has traps set up by Paradise Casino.
Dr. Mark Hoddle, director of the Center for Invasive Species Research and extension specialist at the University of California at Riverside, gave the talk, “South American Palm Weevil — A Threat to the Arizona Palm Industry” at the University of Arizona Yuma Agricultural Center on Feb. 20.
Hoddle gave an overview of the weevil invasion into Tijuana in Baja California, Mexico, and its subsequent northward spread to San Diego County. He noted the weevil was introduced into California as a food.
“It’s pretty good to eat, if you didn’t know what it was. If they put it on a plate, you’d be eating them like calamari.”
The weevil was first brought to the Americas by way of the Caribbean through Egypt, first on coconut palms and then date palms. There was a lot of construction, and live palm trees served as “instant landscaping.”
The insect swept through the Caribbean, made its way to South America, then Central America and now North America. While driving around in Tijuana, Hoddle identified more than 100 dead palm trees and 80 on the California side in one day. They look like “giant brown umbrellas,” he said.
Dead palm trees are catching fire and blowing up electrical wires. They’re also a falling hazard, especially on windy days.
The female weevil uses her snout to drill holes in palm trees where she lays eggs. The pupal cocoons are made from palm fibers. They’re so hard, it’s difficult to open them with fingers.
As the female weevil lays eggs, the trunk of the palm is riddled with holes and hollowed out. The crown becomes unstable, collapses and detaches. It weighs about 250 pounds and can cause significant damage if it falls on top of something or someone.
Palm tree removal costs about $1,500 per tree. Debris from the dead trees can’t be burned. “It’s really hard to set on fire,” Hoddle said.
The recommendation is that debris be run through a chipper and then buried 6 feet below the ground. But there are no regulations in place to make sure that’s being done.
The weevil has killed “hundreds and hundreds” of Canary Island date palms in the Sweetwater Summit Regional Park in Bonita, California. There’s “a lot of food for the weevil” in the park and it’s spreading and killing more palm trees.
Drone surveillance is conducted every four months and monitoring is done by monthly bucket trap checks. The drone surveillance mapped out 686 palms. In March 2017, 51 trees, or 7 percent, had died. In June, 75 trees, or 10 percent, had died. In October, 83 trees, or 11 percent, were dead.
In July 2016, 50 weevils were trapped; now it’s about 245 per month. The number of weevils being trapped is “truly alarming,” Hoddle said.
Infestation seems to start in urban area and then spread to agriculture, he noted, adding, “I suspect it hasn’t established yet.”
The South American palm weevil is moving east,and has been identified in El Cajon, California. Researchers are currently setting up a monitoring program in the Coachella area.
The weevil flies about 15 miles a day, but some reach 25-30 miles a day and even 40 miles “if it put its mind to it.” Some are so desperate to find something to eat, it will kill itself flying, he said.
Hoddle said the seminar was part of an effort to give heads up to Yuma date palm growers so they can prepare because the pest will likely get to this area. If it does, the date industry could be facing a problem.
The South American palm weevil seems to favor the ornamental Canary Island palm trees, probably because they’re “big and fat.” But it doesn’t mean other palm trees are immune. Hoddle believes if they ate all of the Canary Island palms, they would then go on to other types. The weevils in South America go after all the palms, he said.
Another threat to palm trees is the red ring nematode disease, which can also kill the palm. Adult weevils are infected with nematodes when they feed on palm material infected with the disease and then spreads it when they defecate or lay eggs.
“It’s a double whammy,” Hoddle noted. However, red ring disease has not been recorded in the United States.
The best way to protect palm trees from a weevil attack is through the use of pesticides, Hoddle said. A professional arborist can recommend a treatment plan. Anecdotal evidence suggests that in high pressure areas applications should be made every 6 months.
Researchers ask that if someone believes date palm trees on their property have become infected, to report it at http://cisr.ucr.edu/palmarum.html. The website also contains information on how to build a bucket trap.